The bug has been fixed for in version 18.104.22.168
Important for Child Theme users
The @import can be removed from the style.css in the child theme. This is all done in the parent theme. The reason is that this will allow to load the sites faster. See the link for more info.
The example child theme has also been updated.
Please note that guides are just that, guides. Concerning customization guides we cannot assist with implementation at the one on one level and you instead may wish to hire a web pro for hands-on assistance.
So if you have this in your child theme style.css, you will either need to comment it out or remove it:
And if you have a header.php file in your child theme you will need to make sure you either comment or remove any line that looks like this:
<?php wp_enqueue_style('responsive-style', get_stylesheet_uri(), false, '1.7.9'); ?>
Please see the rest of the changes in the changelog.
[!] Fix responsive design bug
Here is the changelog on GitHub
Here is the diff from the trac